I have read all the messages about banging pipes but have not seen my problem. The ganging occurs in the middle of the night, one occurance and for about 5 seconds. I happens frequently although not every night. Since it happens in the night, no appliances are on nor hot water running. It happens with the heat on and AC on. We had a new gas furnace installed and it has happend since then. Incidently, the toilet has a tendency to run and the other bathroom makes a funny noise when flushed. Any advice for a lay person